Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$215.86	11.291%	$240.2328	$240.23	$240.25	$240.20
Purchase #2	$191.33	10.578%	$211.5689	$211.57	$211.55	$211.60
Purchase #3	$52.83	4.348%	$55.127	$55.13	$55.15	$55.10
Purchase #4	$142.29	11.102%	$158.087	$158.09	$158.10	$158.10
Purchase #5	$65.48	3.572%	$67.8189	$67.82	$67.80	$67.80
Purchase #6	$35.63	13.567%	$40.4639	$40.46	$40.45	$40.50
Purchase #7	$50.80	6.523%	$54.1137	$54.11	$54.10	$54.10
7 purchase totals =	$754.22		$827.4122	$827.41	$827.40	$827.40